> I work very hard to provide deep, thoughtful code review

Which is awesome and essential!

But the reason that the value of code reviews drops if they aren't done live, conducted by the person whose code is being reviewed, isn't related to the quality of the feedback. It's because a very large portion of the value of a code review is having the dev who wrote the code walk through it, explaining things, to other devs. At least half the time, that dev will encounter "aha" moments where they see something they have been blind to before, see a better way of doing things, spot discontinuities, etc. That dev has more insight into what went into the code than any other, and this is a way of leveraging that insight.

The modern form of code review, where they are done asynchronously by having reviewers just looking at the code changes themselves, is not worthless, of course. It's just not nearly as useful as the old-school method.